Models for the Asymmetric Enol borinate reduction of a ketone

A key stage in the reaction in the rearrangement of an enol borinate is the C-C bond formation to an aldehyde, mediated by the chiral auxilliary X=di-isopinocampheyl (see I. Paterson et al, Tetrahedron, 1990, 46, p 4663; 1991, 47, pp.3471-3484)

A 3D model for the basic framework (i.e. replacing all substituents with H) of the transition state must be constructed. Since this involves bond formation and cleavage, a QM (Quantum Mechanics) based model must be used, in this case the AM1 semi-empirical method. These calculations reveal that both chair and boat forms of the transition state are possible. The boat transition state is shown below:

View the source code of this document to see how the 3D model is included, both prior to conversion from HTML and after conversion to XHTML. If you are viewing this after the CML conversion process, the model should be present as CML components embedded in the XHTML.